1. Technical Field
The invention relates to a control system incorporated into machinery such as a hand-held meat trimming knife or power operated meat skinning equipment to detect the touch of a bare or gloved human hand upon a conductive surface such as a rotating blade or a rotating feed mechanism in order to provide automated means for protective action against harm to an operator by immediately disconnecting the power drive means from the rotating element.
2. Background Information
Various types of tools have been devised for performing various operations such as power actuated drills, grinders, meat cutting and trimming tools, etc. which are operated by power drive means such as a chain or belt drive from the output shaft of an electric motor, a flexible drive shaft from an electric motor, a power drive shaft from an air motor, for supplying power to the device.
Of these various tools, hand-held power-driven meat cutting knives have been used extensively in the meat industry to facilitate the removal of meat from a carcass primarily in a trimming operation or from removing the meat remains from the bones. These devices are referred to as meat trimming knives and are electrically driven by a flexible drive shaft extending from a remotely mounted electric motor to a pinion gear in the handpiece which rotates an annular cutting blade, or by a pneumatic motor mounted within the handpiece in which the output shaft thereof is connected to the cutting blade by the pinion gear.
Examples of such electrically driven trimming knives using flexible drive shafts are shown in U.S. Pat. Nos. 3,291,010, 4,179,063, 4,178,683, 4,198,750, 4,494,311, and 4,575,938. An example of a pneumatically driven meat trimming knife is shown in U.S. Pat. No. 3,852,882.
Another type of machine used in the meat industry is referred to as a meat skinning machine which may be a floor mounted unit having a horizontally extending rotatable shaft on which is mounted a plurality of teeth located adjacent a skinning knife blade. An operator holds a piece of meat, such as a ham, and presses the meat against the rotating teeth which in combination with the blade removes the skin from the meat.
As with any power operated equipment there is always the danger that the hands or fingers of an operator will come into contact with the rotating knife blade of the hand-held trimming knife, or the rotating toothed feed shaft and adjacent cutting blade of a skinning machine. Therefore to ensure safety to the operator when operating such equipment, he or she will usually wear protective metal mesh gloves of the type shown in U.S. Pat. Nos. 4,384,449, 4,470,251 and 4,004,295. These gloves usually consist of a fine metal mesh covered with strands of a synthetic fiber. The metal mesh prevents or reduces the cutting of the operator upon contacting the cutting blade or toothed meat feed mechanism. Although these metal mesh gloves provide good protection to the operator and have been found to be quite satisfactory for reducing injury to the operator, it is still desirable to provide even greater protection to the operator in certain applications by providing a system which instantaneously removes the power drive source from the rotating element immediately upon contact of the operator's gloved hand with the element or certain other areas of the particular equipment being used by the operator.
Examples of other protective devices and systems for use in reducing injury to the operator are shown in U.S. Pat. No. 941,726, 3,785,230, 4,026,177, 4,391,358, and 4,621,300. Still other types of protective devices provide a mechanism attached to the hands of the operator which automatically pull the operator's hand away from the dangerous part of the equipment upon a certain even occurring. Examples of such safety equipment are shown in U.S. Pat. Nos. 2,978,084; 3,011,610; 3,047,116; 4,195,722; and 4,321,841. However, these safety systems require that the device be attached directly to the operator, requiring the operator to be secured to the equipment and be maintained at the work station.
Still another type of safety control system is shown in German Patent application Serial No. DE 35 01 021.
Although the safety control system of this German device may be satisfactory for certain applications, it requires the operator to remain constantly at the skinning machine or work station, preventing him or her from performing other tasks remote from the work station without first removing the metal gloves. Also, even after contact of the two electrically isolated components and immediate deenergizing of the electric drive motor, there will be some continued movement of the rotating cutting blade or feed roller due to inertia which will continue to draw the operator's gloved hand into the machine possibly causing minor injury. Another problem with this German device is that the machine can be energized and operated without the operator wearing the gloves since energization of the machine does not require the electrical control circuit to first sense the presence of the operator wearing the metal gloves.
It is also desirable in certain applications that the safety device be implemented with a particular meat trimming or skinning machine, but provides freedom of movement for the operator, enabling him or her to walk away from the machine and perform other tasks and then return to the machine without requiring the operator to reconnect directly to the machine by putting the metal gloves back on in order for the safety system to perform satisfactorily.
Therefore, the need exists for an improved safety control system which immediately disconnects the power drive source from a rotating metal component of a meat processing machine and causes reversal of the rotating component in certain applications to prevent injury to the operator upon a metal protective glove worn by the operator contacting the metal component, which provides freedom of movement of the operator from the processing machine by eliminating the need of direct and permanent attachment of the operator to the safety equipment of or component of the machine, and which prevents the machine from being energized unless the operator is wearing the protective metal gloves.